Dimming-lens for headlights.



II. G. CASSADY.

DIMMING. LENS FOR HEADLIVGHTS. APPLICATION FILED Aus. Iu. 1911.

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'ULYSSES Gr. CASSADY, 0F INDIAN AIPQIQIS, INDIANA, ASSIGNOR T0 PRIMOLITE COMPANY, l l

0F INDIANAPOLIS, INDIANA, A CORPORATION 0F INDIANA.

DIMMING-LENS FOB HEADIIIGHTS.

To all whom it may concern Be it known that I, ULYssEs G. CAssADY,

ya citizen of the United States, residing at Indianapolis, in the county of Marion and State of Indiana, have invented a new and useful Dimming-Lens for Headlights, of which the following is a specication.

It is the object of my invention to .produce a diffusing and deflecting lamp glass or lens for automobile headlights, which will prevent the disagreeable and dangerous glare, willf deflect a portion of. the light slightly downward solas to light the road at a suitable distance ahead, will slightly diffuse horizontally this downwardly vdeflected portion of the light so that theilight spot on the road -ahead will be of suitable width tocover the full width of passage for the automobile and wider than` the direct beam of light from the headlight, and will diffuse widely horizontally but very slightly if at all vertically the remainder ofthe light so as to illuminate the sides of the road and the roaditself directly in front of the automobile for some distance ahead. My present'i'nvention. is in some features an improvement on that covered by my Patent No. 1.230,670, granted Junel, 1917, and

-gives'a better distribution and utilization of the light rays, as well as being-easier and less expensive of manufacture:

' The accompanying drawing illustrates my invention. Figure 1 is a-front'elevationofa lamp glass embodying my invention;l Fig. 2'

is asection on the line 2-2 of Fig. ,1; Fig.

and Fig. 4 is an enlarged fragmentary sec-4 tion corresponding to a central part fof l f Fig. 2.

The lamp glass consistsprimarily of a plurality 4of main clear prismatic portions 10 having their front and rear faces relatively oblique and the thin edges of such portions upward, andbetween the thicker lower edge of' each of `these main prismatic portions and the thinner upper edge of the adjacent lower main prismatic portion a series of clear but smaller prismatic portions 11, connecting the two adjacent main por# tions by a series of steps of which each step is itself avprism having light deflecting sur-` to the light.; de-

matic portions. The main prismatic por'- tions 10 and the smaller prismatic portions I' Specification of'Let-ters Patent.

'11 both entend horizontally, across the lamp glass.. At the horizontal ends of these prismatic portions 10 and 11-are `beveled portions 12, which are covered with substan- 10 and the central `parts ofA one or two ofthe next lower main prismatic portions are provided on their. front faces with a series of vvertical ribs 14, which by refraction dif fuse the light passing through them widel horizontally, and only very slightly if at a l vertically, as indicated by Figs. 3,)and 2y respectively. These light diffusing ribs 111 are preferablynotprov'ided on the narrow prlsmatic portions 11, but only on the wide or main prismatic portions 10 near the top of the lamp glass. The beveled portions 12. 'merge into an annular flange 15, whicliin'ay also be provided with radial ribsilwhich this annular flange serve no optical purpose, ordinarily, as this Aflange 15 is merely a. clamping liange and is covered in operation, but serve to prevent the glass from turning in `its frame, so that it will remain yin proper position in spite of the jarring of the associated automobile.

' For convenience in manufacture, the lamp glass is made as one integral piece, convenientlyslightly bulging, so that as awhole itl forms a section of a sphere. The. inner or rear face of the lamp glass is preferably continuous across the various sections 10,11,

enerallyf Each rib J Patented Mar. 26, 11915...l i Application mea August 1o, i917. seriai No. 165,412.

. are continuations of the ribs 13. Thfribr'sfon and 12, and the prisms are formed by l oblique lsurfaces on the frontl face of the lainpglass. The prismatic portions 10 and 11 when the lamp glass is made as a spherical segment as shown, are-curved slightly horizontally, but this does not interfere with the prismatic e'ifect on the `light rays. Byreason of'this prismatic effect, the light rays are deflected obliquely downward through both the prismati portions 10 and the prismatic portions 11, asis clear from Fig. 2. The continuous rear facepof the lamp glass is vertically fluted, as is clear from Fig. 3. The cylindrical surfaces of these flutes 16y produce by refraction a slight dispersion of the light rays horizon rIhe flutes may be either convex or concave, but lt prefer to make them .as conion cave grooves 16 extending vvertically across ,the inner face of the lamp glass, because with concave flutes the foci of the dispersed .light rays are virtual and not real, While I prefer to have the flutes `16 on the rear face and the oblique prism faces on the front face Of theseparallel rays, some pass thrqugh. the clear prisms? 10, some through the small of the lamp glass, this is not essential, and either the flutes or the .oblique faces may be on either or both sides of the lamp glass.

In operation, the lightrays from the lamp 20`strike the reiector 21 and are sent for-k ward as parallel rays, as indicated in Fig. 2.

clear prisms '11,' and some through the ribs 13 and 14. The rays which pass through the clear prismatic` portions 10 and l1 are refracted slightly downward, -as is clear from Fig. 2, because the thin edges of these prismatic portions 1'0 and 11 are upward. The flutes 16, which optically 'are cylinders superposed on the prisms, produce?" also by refraction, a slight horizontal dispersion of these downwardly retracted light rays, as is clear from Fig. 3, so as to produce a light 'spot on the road ahead some distance in front of theautomobile and of the desired width, preferably s uihcient to light something more thanthe full path of passage of The rays which pass' the automobile.

`through the ribs 1,3 and 14: are dispersed,

c j i also by refraction, substantially in planes at right angles to such ribs, with practically no dispersion longitudinally of the ribs. The whole action is one of refraction, for all parts of the lamp glass. The effect of thei flutes 16 onthe rays which pass through the ribs 13 and 14,.though actually the same as upon the rays of light 'which'pass through the clear portions, is in effect` negligible because of the much greater refraction which takes place at such ribs.

As a result of all this, a large portion of the parallel rays from the reflector 2l are deflected slightly downward and spread out .slightly horizontally to produce a light spot i general illumination of the roadsides and to extend it vertically as well as horizontally.

. rlhe angle of this general -illumination is cev greater than 180 both vertically and horizontally, because of the. different angles of the portions 12; but the bulk of the light is used to produce the desired 'light-spot on ,the road ahead or to light the sides ofthe roads, and very little is thrown upward and lost. In addition, lthe cost of manuL l' facture of this) lens where the entire action is by .refraction is much reduced,` because the'lens can bemolded cmplete in one operation, and removed from the mold incondition for immediate use without requiringv any additional-labor. Moreover, all glare from the headlight is eliminated, so that it -does not blind those approaching it.

v A I claim as' my invention:

l. A llamp glass, comprising. a verti-l' prismatic portions having their thin edges uppermost,- and a vertical series of smaller horizontally extending prismatic portions connecting the lower edge of a main prismatic portion with' the adjacent upper edge of thenext lower main prismatic portion by a series of steps, said smaller lprismatic portions beingsub'stantially similar in prismatic effect to the adjacent main prismatic portions. l

2. A lamp glass, comprising a vertical series of main horizontally extending prismatic portions havingv their thin edges, uppermost, and a vertical series of smaller horizontally extending prismatic portions connecting the lower edge of a main prismatic portion with the adjacent upper edge ofthe next lower main prismatic portion by a seriesof steps.-

3. A lamp glass, comprising a vertical series of main horizontally extending prismatic portions having their thin edges uppermost, anda vertical series of smaller horizontally extending prismatic portions connecting thelower edge of a main. prismatic portion with the adjacent upper edge of the next lower main prismatic portion by a series of steps, said smaller prismatic portions being substantially similar in prismatic eiiect to the adjacent main prismatic portions,`said main and smaller prismatic porltions having su'perposed thereon a plurality of vertically extending. cylindrical portions.

V cal series of main horizontally extending 4. A lamp glass, comprising a vertical series of main horizontally extending pris-J matic portions having their thin edges uppermost, and a vertical series of smaller horizontally extending prismatic portions connecting the lower edge of,A a main prismatic portion with the adjacent upper edgeV of the next lower main prismatic portion by a series of steps, said main and smaller prismatic portions having superposed thereno y on a plurality of vertically extending cylindrical portions.

` 5 A lamp glass, comprising a vertical series of' main horizontally extending prismatic portions havin their thin edges uppermost, and a vertical series of smaller horizontally extending prismatic portions 4connectingl the lower edge of a main prismatic portion with the adjacent upper edge ofthe next lower main prismatic portion by a series of. steps, some of said main prismatic portionsbeing provided with a plurality of' narrow vertical ribs which refract the transmitted light widely in a horizontal direc tion. I

6. A lamp glass, comprising a vertical series of main horizontally extending pris-v matic portions having their thin edges uppermost, and a vertical series of smaller horizontally extending prismatic portions connecting the lower edge ofa main prismatic portion with the adjacent upper edge of the next lower main prismatic portion by a series of steps, said lamp glassvbeing provided onpone -face with a plurality of verti-V cal concave flutes of small curvatures and on part of the other face with narrow vertical ribs of great curvature.

7 A lamp glass, comprising a vertical series of main ,horizontally extending prismatic portions having their thin edges uppermost, and a vertical series of smaller ries lof main horizontally extending pris-A -matic portions having their thin edges uppermost, and a vertical series of smaller horizontally extending prismatic portions connecting the lower edge of a main prismatic portion with the adjacent upper edge of the next lower main a series of steps, said lamp glass being proprismatic portion by vided on one face with aA plurality'ofver-l i 'tical 'flutes of `small curvature which cross both thev main and smaller prismatic portions, and von part of the other face with narrow vertical ribs of great curvature.

9.' A lamp glass comprising a vertical series of horizontally extending light-transmitting prismatic portionshaving. their thin edges uppermost, some but less than all of said portions being provided with vertical ribs of great curvature so as to produce a wide horizontal light diffusion, and others of said portions iheing clear of such ribs so that they transmit the light Without producsuch wide horizontal lightdiffusion.

n witness whereof, I have hereunto set my hand at Indianapolis," Indiana,- this seventh day of August, A`.D. one thousand nine hundred and seventeen.

vunvssns ecassanv. 

